Research article - Peer-reviewed, 2008
Cation exchange in forest soils: the need for a new perspectiveRoss, D. S.; Matschonat, G.; Skyllberg, U.
AbstractThe long-term sustainability of forest soils may be affected by the retention of exchangeable nutrient cations such as Ca(2+) and the availability of potentially toxic cations such as Al(3+). Many of our current concepts of cation exchange and base cation saturation are largely unchanged since the beginnings of soil chemistry over a century ago. Many of the same methods are still in use even though they were developed in a period when exchangeable aluminium (Al) and variable charge were not generally recognized. These concepts and methods are not easily applicable to acid, highly organic forest soils. The source of charge in these soils is primarily derived from organic matter (OM) but the retention of cations, especially Al species, cannot be described by simple exchange phenomena. In this review, we trace the development of modern cation exchange definitions and procedures, and focus on how these are challenged by recent research on the behaviour of acid forest soils. Although the effective cation exchange capacity (CECe) in an individual forest soil sample can be easily shown to vary with the addition of strong base or acid, it is difficult to. and a pH effect in a population of different acid forest soil samples. In the very acidic pH range below ca 4.5, soils will generally have smaller concentrations of adsorbed Al(3+). This can be ascribed to a reduced availability of weatherable Al-containing minerals and a large amount of weak, organic acidity. Base cation saturation calculations in this pH range do not provide a useful metric and, in fact, pH is modelled better if Al(3+) is considered to be a base cation. Measurement of exchangeable Al(3+) with a neutral salt represents an ill-defined but repeatable portion of organically complexed Al, affected by the pH of the extractant. Cation exchange in these soils can be modelled if assumptions are made as to the proportion of individual cations that are non-specifically bound by soil OM. Future research should recognize these challenges and focus on redefining our concepts of cation retention in these important soils.
Published inEuropean Journal of Soil Science
2008, volume: 59, number: 6, pages: 1141-1159
Publisher: BLACKWELL PUBLISHING
Ross, D. S.
University of Vermont
University of Hohenheim
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Sustainable Development Goals
SDG15 Life on land
UKÄ Subject classification
Environmental Sciences related to Agriculture and Land-use
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